Shaft seals for rotating machines, such as the rotor of a centrifugal compressor, present several design challenges. For example, the seal oil used in oil film seals has a tendency to migrate to the interior of the machine and contaminate the working fluid. Also, in the case of a compressor, the working fluid to be compressed often escapes into the seal, thereby wasting valuable product and achieving loss of performance.
Since both of these problems typically reduce the efficiency of the rotating machinery, they are continuously addressed and improved upon. Remedial techniques include venting or piping the leaked oil and/or gas to a low pressure point where it can be either used in a lower-pressure machine or flared to the environment. Both of these techniques, however, can result in relatively large losses of oil and a rather high degree of pollution emitted into the atmosphere.
What is needed, therefore, is a shaft seal system that eliminates the need to vent leaked oil and/or gas to a low-pressure point or flare the leaked fluids into the environment.